If the initial acid is polybasic, then the formation of either full esters is possible - all HO groups are replaced, or acid esters - partial substitution. For monobasic acids, only full esters are possible (Fig. 1).
Rice. one. EXAMPLES OF ESTERS based on inorganic and carboxylic acids
Esters nomenclature. The name is created as follows: first the group is indicated R , attached to the acid, then - the name of the acid with the suffix "at" (as in the names of inorganic salts: carbon at sodium, nitr at chromium). Examples in fig.2
If one uses the trivial ( cm. TRIVIAL NAMES OF SUBSTANCES) the name of the starting acid, then the word “ether” is included in the name of the compound, for example, C 3 H 7 COOC 5 H 11 is the amyl ester of butyric acid.
Classification and composition of esters. Among the studied and widely used esters, the majority are compounds derived from carboxylic acids. Esters based on mineral (inorganic) acids are not so diverse, because the class of mineral acids is less numerous than carboxylic acids (the variety of compounds is one of hallmarks organic chemistry).When the number of C atoms in the initial carboxylic acid and alcohol does not exceed 6–8, the corresponding esters are colorless oily liquids, most often with a fruity odor. They form a group of fruit esters. If an aromatic alcohol (containing an aromatic nucleus) is involved in the formation of an ester, then such compounds, as a rule, have a floral rather than a fruity odor. All compounds of this group are practically insoluble in water, but readily soluble in most organic solvents. These compounds are interesting for a wide range of pleasant aromas (Table 1), some of them were first isolated from plants and later synthesized artificially.
| Tab. one. SOME ESTERS, with a fruity or floral aroma (fragments of the starting alcohols in the formula of the compound and in the name are in bold type) | ||
| Ester Formula | Name | Aroma |
| CH 3 SOO C 4 H 9 | Butyl acetate | pear |
| C 3 H 7 COO CH 3 | Methyl butyric acid ester | apple |
| C 3 H 7 COO C 2 H 5 | Ethyl butyric acid ester | pineapple |
| C 4 H 9 COO C 2 H 5 | Ethyl | crimson |
| C 4 H 9 COO C 5 H 11 | Isoamil isovaleric acid ester | banana |
| CH 3 SOO CH 2 C 6 H 5 | Benzyl acetate | jasmine |
| C 6 H 5 SOO CH 2 C 6 H 5 | Benzyl benzoate | floral |
The third group is fats. Unlike the previous two groups based on monohydric alcohols
ROH , all fats are esters of the alcohol glycerol HOCH 2 -CH (OH) -CH 2 OH. Carboxylic acids, which are part of fats, as a rule, have a hydrocarbon chain with 9-19 carbon atoms. Animal fats (cow butter, lamb, lard) are plastic, fusible substances. Vegetable fats (olive, cottonseed, sunflower oil) are viscous liquids. Animal fats mainly consist of a mixture of stearic and palmitic acid glycerides (Fig. 3A, B). Vegetable oils contain glycerides of acids with a slightly shorter carbon chain: lauric C 11 H 23 COOH and myristic C 13 H 27 COOH. (like stearic and palmitic are saturated acids). Such oils can be stored in air for a long time without changing their consistency, and therefore are called non-drying. In contrast, linseed oil contains unsaturated linoleic acid glyceride (Fig. 3B). When applied in a thin layer to the surface, such an oil dries out under the action of atmospheric oxygen during polymerization according to double bonds, thus forming an elastic film, insoluble in water and organic solvents. Based linseed oil produce natural drying oil.
Rice. 3. GLYCERIDES OF STEARIC AND PALMITIC ACID (A AND B)- components of animal fat. Linoleic acid glyceride (B) is a component of linseed oil.
Esters of mineral acids (alkyl sulfates, alkyl borates containing fragments of lower alcohols C 1–8) are oily liquids, esters of higher alcohols (starting with C 9) are solid compounds.
Chemical properties of esters. The most typical for esters of carboxylic acids is the hydrolytic (under the action of water) cleavage of the ester bond; in a neutral medium, it proceeds slowly and noticeably accelerates in the presence of acids or bases, because H+ and HO– ions catalyze this process (Fig. 4A), with hydroxide ions acting more efficiently. Hydrolysis in the presence of alkalis is called saponification. If we take an amount of alkali sufficient to neutralize all the acid formed, then complete saponification of the ester occurs. Such a process is carried out on an industrial scale, and glycerol and higher carboxylic acids (С15–19) are obtained in the form of alkali metal salts, which are soaps (Fig. 4B). The fragments of unsaturated acids contained in vegetable oils, like any unsaturated compounds, can be hydrogenated, hydrogen is added to double bonds, and compounds similar to animal fats are formed (Fig. 4B). In this way, solid fats are obtained in industry based on sunflower, soybean or corn oil. Margarine is made from vegetable oil hydrogenation products mixed with natural animal fats and various food additives.The main method of synthesis is the interaction of a carboxylic acid and an alcohol, catalyzed by an acid and accompanied by the release of water. This reaction is the opposite of that shown in Fig. 3A. In order for the process to go in the right direction (ester synthesis), water is distilled (distilled off) from the reaction mixture. Special studies using labeled atoms, it was possible to establish that during the synthesis, the O atom, which is part of the resulting water, is detached from the acid (marked with a red dotted frame), and not from alcohol (an unrealized variant is highlighted with a blue dotted frame).
Esters of inorganic acids, for example, nitroglycerin, are obtained according to the same scheme (Fig. 5B). Instead of acids, acid chlorides can be used; the method is applicable to both carboxylic (Fig. 5C) and inorganic acids (Fig. 5D).
Interaction of salts of carboxylic acids with haloalkyls
RCl also leads to esters (Fig. 5D), the reaction is convenient in that it is irreversible - the liberated inorganic salt immediately removed from the organic reaction medium in the form of a precipitate.The use of esters. Ethyl formate HCOOS 2 H 5 and ethyl acetate H 3 COOS 2 H 5 are used as solvents for cellulose varnishes (based on nitrocellulose and cellulose acetate).Esters based on lower alcohols and acids (Table 1) are used in the food industry to create fruit essences, and esters based on aromatic alcohols in the perfume industry.
Polishes, lubricants, impregnating compositions for paper (waxed paper) and leather are made from waxes, they are also part of cosmetic creams and medicinal ointments.
Fats, together with carbohydrates and proteins, make up a set of nutritionally necessary food products, they are part of all plant and animal cells, in addition, accumulating in the body, they play the role of an energy reserve. Due to the low thermal conductivity, the fat layer well protects animals (especially marine ones - whales or walruses) from hypothermia.
Animal and vegetable fats are raw materials for the production of higher carboxylic acids, detergents, and glycerin (Fig. 4), which is used in the cosmetics industry and as a component of various lubricants.
Nitroglycerin (Fig. 4) is a well-known drug and explosive, the basis of dynamite.
On the basis of vegetable oils, drying oils are made (Fig. 3), which form the basis of oil paints.
Sulfuric acid esters (Fig. 2) are used in organic synthesis as alkylating agents (introducing an alkyl group into the compound), and phosphoric acid esters (Fig. 5) are used as insecticides, as well as additives to lubricating oils.
Mikhail Levitsky
LITERATURE Kartsova A.A. The conquest of matter. Organic chemistry . Publishing house Himizdat, 1999Pustovalova L.M. Organic chemistry. Phoenix, 2003
Fats and oils are natural esters that are formed by a trihydric alcohol - glycerol and higher fatty acids with an unbranched carbon chain containing even number carbon atoms. In turn, sodium or potassium salts of higher fatty acids are called soaps.
When carboxylic acids interact with alcohols ( esterification reaction) esters are formed:
This reaction is reversible. The reaction products can interact with each other to form the initial substances - alcohol and acid. Thus, the reaction of esters with water - ester hydrolysis - is the reverse of the esterification reaction. Chemical equilibrium, which is established when the rates of direct (esterification) and reverse (hydrolysis) reactions are equal, can be shifted towards the formation of ether by the presence of water-removing agents.
Esters in nature and technology
Esters are widely distributed in nature and are used in engineering and various industries. They are good solvents organic substances, their density is less than the density of water, and they practically do not dissolve in it. Thus, esters with a relatively small molecular weight are highly flammable liquids with low boiling points and smell of various fruits. They are used as solvents for varnishes and paints, flavorings of food industry products. For example, butyric acid methyl ester has the smell of apples, the ethyl ester of this acid has the smell of pineapples, isobutyl ester of acetic acid has the smell of bananas:
Esters of higher carboxylic acids and higher monobasic alcohols are called waxes. So, beeswax is the main
together from an ester of palmitic acid and myricyl alcohol C 15 H 31 COOC 31 H 63 ; sperm whale wax - spermaceti - an ester of the same palmitic acid and cetyl alcohol C 15 H 31 COOC 16 H 33.
Fats
The most important representatives of esters are fats.
Fats- natural compounds that are esters of glycerol and higher carboxylic acids.
The composition and structure of fats can be reflected by the general formula:
Most fats are formed by three carboxylic acids: oleic, palmitic and stearic. Obviously, two of them are limiting (saturated), and oleic acid contains a double bond between carbon atoms in the molecule. Thus, the composition of fats can include residues of both saturated and unsaturated carboxylic acids in various combinations.
AT normal conditions fats containing residues of unsaturated acids in their composition are most often liquid. They are called oils. Mostly fats plant origin- linseed, hemp, sunflower and other oils. Less common are liquid fats of animal origin, such as fish oil. Most natural fats of animal origin under normal conditions are solid (fusible) substances and contain mainly residues of saturated carboxylic acids, for example, mutton fat. So, palm oil is a solid fat under normal conditions.
The composition of fats determines their physical and chemical properties. It is clear that for fats containing residues of unsaturated carboxylic acids, all reactions of unsaturated compounds are characteristic. They discolor bromine water, enter into other addition reactions. The most important reaction in practical terms is the hydrogenation of fats. Solid esters are obtained by hydrogenation of liquid fats. It is this reaction that underlies the production of margarine, a solid fat from vegetable oils. Conventionally, this process can be described by the reaction equation:
hydrolysis:
Soaps
All fats, like other esters, undergo hydrolysis. The hydrolysis of esters is a reversible reaction. To shift the equilibrium towards the formation of hydrolysis products, it is carried out in an alkaline environment (in the presence of alkalis or Na 2 CO 3). Under these conditions, the hydrolysis of fats proceeds irreversibly and leads to the formation of salts of carboxylic acids, which are called soaps. Hydrolysis of fats in an alkaline environment is called saponification of fats.
When fats are saponified, glycerol and soaps are formed - sodium or potassium salts of higher carboxylic acids:
Crib
Derivatives of carboxylic or inorganic acids in which the hydrogen atom in the hydroxyl group is replaced by a radical are called esters. Usually the general formula of esters is denoted as two hydrocarbon radicals attached to a carboxyl group - C n H 2n + 1 -COO-C n H 2n + 1 or R-COOR '.
Nomenclature
The names of esters are made up of the names of the radical and acid with the suffix "-at". For example:
- CH3COOH- methyl formate;
- HCOOCH 3- ethyl formate;
- CH 3 COOC 4 H 9- butyl acetate;
- CH 3 -CH 2 -COO-C 4 H 9- butylpropionate;
- CH 3 -SO 4 -CH 3- dimethyl sulfate.
The trivial names of the acid that is part of the compound are also used:
- S 3 H 7 COOS 5 H 11- amyl ester of butyric acid;
- HCOOCH 3- methyl ester of formic acid;
- CH 3 -COO-CH 2 -CH (CH 3) 2- isobutyl ester of acetic acid.
Rice. one. Structural formulas esters with names.
Classification
Esters are divided into two groups depending on their origin:
- esters of carboxylic acids- contain hydrocarbon radicals;
- esters of inorganic acids- include the rest of mineral salts (C 2 H 5 OSO 2 OH, (CH 3 O)P(O)(OH) 2 , C 2 H 5 ONO).
The most diverse esters of carboxylic acids. Their complexity depends on the complexity of the structure. physical properties. Esters of lower carboxylic acids are volatile liquids with a pleasant aroma, higher carboxylic acids are solids. These are poorly soluble compounds floating on the surface of the water.
Types of esters of carboxylic acids are shown in the table.
|
View |
Description |
Examples |
|
fruit esters |
Liquids whose molecules contain no more than eight carbon atoms. They have a fruity aroma. Composed of monohydric alcohols and carboxylic acids |
|
|
Liquid (oils) and solids containing from nine to 19 carbon atoms. Composed of glycerol and residues of carboxylic (fatty) acids |
Olive oil - a mixture of glycerin with residues of palmitic, stearic, oleic, linoleic acids |
|
|
Solids with 15-45 carbon atoms |
CH 3 (CH 2) 14 -CO-O- (CH 2) 29 CH 3-myricyl palmitate |
Rice. 2. Wax.
Esters of carboxylic acids are the main component of aromatic essential oils found in fruits, flowers, and berries. Also included in beeswax.
Rice. 3. Essential oils.
Receipt
Esters are obtained in several ways:
- esterification reaction of carboxylic acids with alcohols:
CH 3 COOH + C 2 H 5 OH → CH 3 COOC 2 H 5 + H 2 O;
- reaction of carboxylic acid anhydrides with alcohols:
(CH 3 CO) 2 O + 2C 2 H 5 OH → 2CH 3 COOC 2 H 5 + H 2 O;
- the reaction of salts of carboxylic acids with halocarbons:
CH 3 (CH 2) 10 COONa + CH 3 Cl → CH 3 (CH 2) 10 COOCH 3 + NaCl;
- addition reaction of carboxylic acids to alkenes:
CH 3 COOH + CH 2 \u003d CH 2 → CH 3 COOCH 2 CH 3 + H 2 O.
Properties
Chemical properties esters are due functional group-COOH. The main properties of esters are described in the table.
Esters are used in cosmetology, medicine, food industry as flavors, solvents, fillers.
What have we learned?
From the topic of the 10th grade chemistry lesson, we learned what esters are. These are compounds containing two radicals and a carboxyl group. Depending on the origin, they may contain residues of mineral or carboxylic acids. Esters of carboxylic acids are divided into three groups: fats, waxes, fruit esters. These are poorly soluble substances in water with a low density and a pleasant aroma. Esters react with alkalis, water, halogens, alcohols and ammonia.
Topic quiz
Report Evaluation
Average rating: 4.6. Total ratings received: 89.
Esters are derivatives of oxo acids (both carboxylic and mineral) RkE (= O) l (OH) m, (l ≠ 0), which are formally products of substitution of hydrogen atoms of hydroxyls -OH of the acid function for a hydrocarbon residue (aliphatic, alkenyl, aromatic or heteroaromatic); are also considered as acyl derivatives of alcohols. In the IUPAC nomenclature, esters also include acyl derivatives of chalcogenide analogs of alcohols (thiols, selenols, and tellurols)
They differ from ethers, in which two hydrocarbon radicals are connected by an oxygen atom (R1-O-R2).
General formula esters:
Esters nomenclature.
The name is created as follows: first, the R group attached to the acid is indicated, then the name of the acid with the suffix "at" (as in the names of inorganic salts: carbon at sodium, nitr at chromium). Examples in fig. 2
Rice. 2. NAMES OF ESTERS. Fragments of molecules and their corresponding fragments of names are highlighted in the same color. Esters are usually thought of as reaction products between an acid and an alcohol, for example, butyl propionate can be thought of as the reaction product of propionic acid and butanol.
If the trivial name of the starting acid is used, then the word “ether” is included in the name of the compound, for example, C 3 H 7 COOC 5 H 11 is the amyl ester of butyric acid.
homologous series esters.
The general formula of esters is R1--CO---R2, where R1 and R2 are carbohydrate radicals. Esters are derivatives of acids in which H in the hydroxyl is replaced by a radical. Esters are named after acids and alcohols. who are involved in education
H-CO-O-CH3-- methyl formate or formic acid methyl ester or formic methyl ester.
CH3-CO-O-C2H5 - ethyl acetate or ethyl ester of acetic acids or, acetic ethyl ester..
C3H7-CO-O-CH3 - butyric acid methyl ester or methyl butyrate
С3Н7-СО-О-С2Н5 - butyric acid ethyl ester or ethyl butyrate
In short, you need to write off the table of carboxylic acids. and to them the name of the salt (formic - formate, acetic - acetate, propionic - propinate. Butyrate, valeric - valeriate, caproic - capronate., enanthic - enanthonate, oxalic - oxalate. malonic - malonate. succinic - succinate .... Look how the names of the ethers are formed.
CH3- CO-O (this is acetic acid without H) --C5H11- (this is the monovalent radical pentyl (amyl) - table) this is the name of this ester.
Acetic amyl ester, amine ester of acetic acid. amyl acetate. See more.
CH3CH2CH2CH2-CO-O (pentanoic or valeric acid) --- C4H9 (this is butyl) - butyl valerate, valerian-butyl ester, butyl ester of valeric acid.
Isomerism.
Esters are characterized by isomerism of the hydrocarbon skeleton. For example, propyl acetate and isopropyl acetate are isomers. Since the ester molecule contains two hydrocarbon radicals - in the acid residue and in the alcohol residue - then isomerism of each of the radicals is possible. For example, propyl acetate and isopropyl acetate (alcohol isomerism) or ethyl butyrate and ethyl isobutyrate (acid radical isomerism) are isomers.
physical properties. Esters are colorless liquids, slightly soluble or completely insoluble in water, have a specific odor (in small concentrations - pleasant, often fruity or floral). Esters of higher alcohols and higher acids are solids.
Chemical properties . The most characteristic reaction for esters is hydrolysis. Hydrolysis occurs in the presence of acids or alkalis. When an ester is hydrolyzed in the presence of acids, a carboxylic acid and an alcohol are formed:
During the hydrolysis of an ester in the presence of alkalis, a salt of a carboxylic acid and an alcohol are formed:
Ways to get.
Methods for obtaining esters. Main products and areas of their application. Conditions for the reaction of esterification of organic acids with alcohols. process catalysts. Peculiarities technological design esterification reaction site.
1. Interaction of acids with alcohols:
This is the most common way to obtain esters.
2. Synthesis of esters by aldehyde condensation:
The synthesis of esters from aldehydes (Tishchenko's reaction) is carried out in the presence of aluminum alcoholate activated with iron chloride or, better, with aluminum chloride and zinc oxide. This method is of industrial importance.
3. Addition of organic acids to alkenes:
4. Synthesis of esters by dehydrogenation of alcohols:
5. Obtaining esters by the method of interesterification.
This reaction has two varieties: the exchange reaction between ether and alcohol by alcohol radicals (alcoholysis reaction):
and the exchange reaction of acid radicals at the alcohol group of the ester:
6. Synthesis of esters from acid anhydrides and alcohols:
7. Interaction of ketones with alcohols:
8. Interaction between acid halides and alcohols:
9. Reaction between silver or potassium salts of acids and aliphatic halogen derivatives:
10. Reaction of acids with aliphatic diazo compounds
Application.
Some esters are used as solvents (ethyl acetate is of the greatest practical importance). Due to their pleasant smell, many esters are used in the food and cosmetic industries. Esters of unsaturated acids are used for the production of Plexiglas, the most widely used for this purpose is methyl methacrylate.
On the topic
"Ethers and Complexes"
Completed by: Manzhieva A.A.
If the initial acid is polybasic, then the formation of either full esters is possible - all HO groups are replaced, or acid esters - partial substitution. For monobasic acids, only full esters are possible (Fig. 1).
Rice. one. EXAMPLES OF ESTERS based on inorganic and carboxylic acids
Esters nomenclature.
The name is created as follows: first, the R group attached to the acid is indicated, then the name of the acid with the suffix "at" (as in the names of inorganic salts: carbon at sodium, nitr at chromium). Examples in fig. 2
Rice. 2. NAMES OF ESTERS. Fragments of molecules and their corresponding fragments of names are highlighted in the same color. Esters are usually thought of as reaction products between an acid and an alcohol, for example, butyl propionate can be thought of as the reaction product of propionic acid and butanol.
If one uses the trivial ( cm. TRIVIAL NAMES OF SUBSTANCES) the name of the starting acid, then the word “ether” is included in the name of the compound, for example, C 3 H 7 COOC 5 H 11 is the amyl ester of butyric acid.
Classification and composition of esters.
Among the studied and widely used esters, the majority are compounds derived from carboxylic acids. Esters based on mineral (inorganic) acids are not so diverse, because the class of mineral acids is less numerous than carboxylic acids (the variety of compounds is one of the hallmarks of organic chemistry).
When the number of C atoms in the initial carboxylic acid and alcohol does not exceed 6–8, the corresponding esters are colorless oily liquids, most often with a fruity odor. They form a group of fruit esters. If an aromatic alcohol (containing an aromatic nucleus) is involved in the formation of an ester, then such compounds, as a rule, have a floral rather than a fruity odor. All compounds of this group are practically insoluble in water, but readily soluble in most organic solvents. These compounds are interesting for a wide range of pleasant aromas (Table 1), some of them were first isolated from plants and later synthesized artificially.
| Tab. one. SOME ESTERS, with a fruity or floral aroma (fragments of the starting alcohols in the formula of the compound and in the name are in bold type) | ||
| Ester Formula | Name | Aroma |
| CH 3 SOO C 4 H 9 | Butyl acetate | pear |
| C 3 H 7 COO CH 3 | Methyl butyric acid ester | apple |
| C 3 H 7 COO C 2 H 5 | Ethyl butyric acid ester | pineapple |
| C 4 H 9 COO C 2 H 5 | Ethyl | crimson |
| C 4 H 9 COO C 5 H 11 | Isoamil isovaleric acid ester | banana |
| CH 3 SOO CH 2 C 6 H 5 | Benzyl acetate | jasmine |
| C 6 H 5 SOO CH 2 C 6 H 5 | Benzyl benzoate | floral |
With an increase in the size of the organic groups that make up the esters, up to C 15–30, the compounds acquire the consistency of plastic, easily softened substances. This group is called waxes and is generally odorless. Beeswax contains a mixture of various esters, one of the components of the wax, which was able to isolate and determine its composition, is myricyl ester of palmitic acid C 15 H 31 COOC 31 H 63 . Chinese wax (a product of the isolation of cochineal - insects of East Asia) contains ceryl ester of cerotinic acid C 25 H 51 COOS 26 H 53. In addition, waxes contain both free carboxylic acids and alcohols, including large organic groups. Waxes are not wetted by water, soluble in gasoline, chloroform, benzene.
The third group is fats. Unlike the previous two groups based on ROH monohydric alcohols, all fats are esters formed from the trihydric alcohol glycerol HOCH 2 -CH (OH) -CH 2 OH. Carboxylic acids, which are part of fats, as a rule, have a hydrocarbon chain with 9-19 carbon atoms. Animal fats (cow butter, lamb, lard) are plastic, fusible substances. Vegetable fats (olive, cottonseed, sunflower oil) are viscous liquids. Animal fats mainly consist of a mixture of stearic and palmitic acid glycerides (Fig. 3A, B). Vegetable oils contain glycerides of acids with a slightly shorter carbon chain: lauric C 11 H 23 COOH and myristic C 13 H 27 COOH. (like stearic and palmitic are saturated acids). Such oils can be stored in air for a long time without changing their consistency, and therefore are called non-drying. In contrast, linseed oil contains unsaturated linoleic acid glyceride (Fig. 3B). When applied in a thin layer to the surface, such an oil dries out under the action of atmospheric oxygen during the polymerization of double bonds, and an elastic film is formed that is insoluble in water and organic solvents. On the basis of linseed oil, natural drying oil is made.
Rice. 3. GLYCERIDES OF STEARIC AND PALMITIC ACID (A AND B)- components of animal fat. Linoleic acid glyceride (B) is a component of linseed oil.
Esters of mineral acids (alkyl sulfates, alkyl borates containing fragments of lower alcohols C 1–8) are oily liquids, esters of higher alcohols (starting with C 9) are solid compounds.
Chemical properties of esters.
The most typical for esters of carboxylic acids is the hydrolytic (under the action of water) cleavage of the ester bond; in a neutral medium, it proceeds slowly and noticeably accelerates in the presence of acids or bases, because H+ and HO– ions catalyze this process (Fig. 4A), with hydroxide ions acting more efficiently. Hydrolysis in the presence of alkalis is called saponification. If we take an amount of alkali sufficient to neutralize all the acid formed, then complete saponification of the ester occurs. Such a process is carried out on an industrial scale, and glycerol and higher carboxylic acids (С15–19) are obtained in the form of alkali metal salts, which are soaps (Fig. 4B). The fragments of unsaturated acids contained in vegetable oils, like any unsaturated compounds, can be hydrogenated, hydrogen is added to double bonds, and compounds similar to animal fats are formed (Fig. 4B). In this way, solid fats are obtained in industry based on sunflower, soybean or corn oil. Margarine is made from vegetable oil hydrogenation products mixed with natural animal fats and various food additives.
The main method of synthesis is the interaction of a carboxylic acid and an alcohol, catalyzed by an acid and accompanied by the release of water. This reaction is the opposite of that shown in Fig. 3A. In order for the process to go in the right direction (ester synthesis), water is distilled (distilled off) from the reaction mixture. Special studies using labeled atoms made it possible to establish that during the synthesis, the O atom, which is part of the resulting water, is detached from the acid (marked with a red dotted frame), and not from alcohol (an unrealized variant is highlighted with a blue dotted frame).
Esters of inorganic acids, for example, nitroglycerin, are obtained according to the same scheme (Fig. 5B). Instead of acids, acid chlorides can be used; the method is applicable to both carboxylic (Fig. 5C) and inorganic acids (Fig. 5D).
The interaction of salts of carboxylic acids with haloalkyls RCl also leads to esters (Fig. 5D), the reaction is convenient because it is irreversible - the released inorganic salt is immediately removed from the organic reaction medium in the form of a precipitate.
The use of esters.
Ethyl formate HCOOS 2 H 5 and ethyl acetate H 3 COOS 2 H 5 are used as solvents for cellulose varnishes (based on nitrocellulose and cellulose acetate).
Esters based on lower alcohols and acids (Table 1) are used in the food industry to create fruit essences, and esters based on aromatic alcohols are used in the perfume industry.
Polishes, lubricants, impregnating compositions for paper (waxed paper) and leather are made from waxes, they are also part of cosmetic creams and medicinal ointments.
Fats, together with carbohydrates and proteins, make up a set of food products necessary for nutrition, they are part of all plant and animal cells, in addition, accumulating in the body, they play the role of an energy reserve. Due to the low thermal conductivity, the fat layer well protects animals (especially marine ones - whales or walruses) from hypothermia.
Animal and vegetable fats are raw materials for the production of higher carboxylic acids, detergents, and glycerin (Fig. 4), which is used in the cosmetics industry and as a component of various lubricants.
Nitroglycerin (Fig. 4) is a well-known drug and explosive, the basis of dynamite.
On the basis of vegetable oils, drying oils are made (Fig. 3), which form the basis of oil paints.
Sulfuric acid esters (Fig. 2) are used in organic synthesis as alkylating agents (introducing an alkyl group into the compound), and phosphoric acid esters (Fig. 5) are used as insecticides, as well as additives to lubricating oils.
Mikhail Levitsky